The present invention generally relates to a storage apparatus and its data transfer method, and in particular relates to a storage apparatus configured from a controller comprising individual I/Os (referring to data transfer paths; hereinafter the same) to a cache memory, a host, and an HDD (Hard Disk Drive), and its data transfer method.
Conventionally, a storage apparatus configures a host interface, a cache memory, and a drive interface connected to an HDD, a controller for controlling the data transfer, an I/O for connecting the foregoing components, and a microprocessor for controlling the overall system as a single unit (module), and connects a plurality of modules with a dedicated I/O. Each module has an independent power supply, and host transfer data is subject to storing to a cache memory of the other module in order to improve the reliability against data loss (for instance, refer to Japanese Patent Laid-Open Publication No. 2005-44010).
Meanwhile, there are cases where the storage apparatus is configured to expand hosts and HDD drives by connecting a plurality of modules. With data transfer through the I/O, there are cases where the I/O between modules to be routed can be selected even if the transfer source and the transfer destination are the same. Accordingly, with a storage apparatus, an optimal path selection (routing) is possible according to the transfer status and failure status of each I/O. As one example of a path selection method, Japanese Patent Laid-Open Publication No. H11-313069 discloses a method of selecting the optimal path by weighting in accordance with the usage status in the connection of nodes; that is, the connection of controllers, and selecting the optimal path from the weighted sum between the nodes included between the transfer source and the transfer destination.